Check out the Super Cheap and Super Slim iFcane E1 Phone

The iFcane E1 is designed to be as portable as a Credit Card and fits in your wallet. Besides making calls, it supports Bluetooth, MP3, FM radio, alarm clock, etc. No games or Internet access, it's suitable for kids or students. It has a unique 5.8mm super slim profile.

Features

• The world's lightest and smallest mobile phone, weighs only 35g with the thickness of only 5.8mm.
• Support Bluetooth, MP3, FM radio, alarm clock, etc.
• No games or Internet access, suitable for kids or students.
• 7 days ultra long standby time.
• 1-inch energy saving LED screen.
• Full mute function allows to use it in quiet occasions.

According to review of Boba Fett who bought the phone on Amazon, It is an awesome phone.

He said; I bought the "upgrade" model recently and it feels much more solidly built; the whole back cover snaps off instead of a flimsy, finicky half-panel that slides off on the regular model, the way the SIM and MicroSD slot in are much better, and the cover goes on snugly over them, all of which solves my main issue with the regular model. I am changing my review to five stars for the "Upgrade" version. (to which this review was attached by Amazon (initially incorrectly) in any case) The "regular" E1 was five or six bucks cheaper (and still keeps 4 stars from me) but I would recommend that everyone go for the "upgrade" model. *

I hate smart phones and I will never use one as long as I live. The dumber the better is my phone motto.
This phone has no camera, no internet, no nothing. Perfect.
It makes and receives phone calls, sends and receives picture-free text messages, has a basic and handy alarm and calendar functionality.
The screen is very bright and legible (blue on black, I think it's OLED) and the old-skool directional-button interface completely intuitive to people like me who consider swiping and multi-touch and all that jazz stupid and gimmicky.
It plays MP3s from a microSD card.
It has Bluetooth but I have never tried using it.
It weighs less than a pack of gum. And it costs not much more than a movie ticket.
It is basically the perfect phone if you hate the idea of you and/or your loved ones being in thrall to a smartphone.
The only reason I give it four stars rather than five is that it is made of flimsy plastic and the battery cover won't go on right once the SIM chip (uses full size) is inserted. Still, the cover has never fallen off, it just leaves a little gap.
And the battery life is not great in standby mode considering how little power it must use... the battery must be really tiny.

Standby time is maybe four days max. I have never spent tons of continuous talk time on it so hard to say how many hours it would last flat out. However, you could charge it in no time from any portable power bank, which come very cheap these days. I bet one of those lipstick sized power banks could charge this phone many times on a single charge.

IMPORTANT: This is a 2G GSM phone. It will work on ATT network only until the end of the year. After that, it will only work on T-Mobile (or providers using their network). Since I love T-Mobile, that's a win. ATT shutting down its 2G is just another sign it hates its customers.
This phone should work in most countries in the world with GSM, given the right SIM. Not Japan though. No GSM there. Do your research if you plan to use it internationally (I haven't yet but I would not hesitate to take one overseas, maybe two for a spare).

Another User Amen Zwa says it is the perfect phone for Child safety.               She say: I needed a small, basic phone for my preteen, so that he can make calls in case of emergency, while on school field trips. I do not wish to expose my son to the hazards that attend a smart phone, and I think it unkind to saddle him with a senior-citizen flip phone. So, I purchased the E1 card phone for him, and it is the right choice for the purpose.

The phone arrived within a week. And a few minutes at a local AT&T store was all it took to activate this GSM phone with a prepaid SIM card. Call quality is acceptable. Ringer is loud enough to be heard, while the phone is stowed in a backpack compartment. The 480x320 colour LCD display is usable. The phone is capable of text messaging, but the T9 text input and the small display combination is appropriately inconvenient to use, so there is no concern of texting being a distraction.

Obviously, this basic phone has no built-in GPS receiver, so the child's location cannot be tracked with AT&T FamilyMap. But, of course, the E911 service can locate the phone with reasonable precision, using cellular triangulation. Note, though, that because this phone is only about 2 mm thick, it might be a bit too delicate for younger children.